FI86837C - Method and apparatus for making glass in water oven - Google Patents

Description

1 86837

Method of making glass in the bath oven and the equipment intended for it - Förfarande och anordning för framställning av glas i vannugn.

The invention relates to the production of glass in continuous equipment, i.e. in which the various steps of the process leading to the production of a material suitable for molding, mainly smelting, processing and processing, take place during relatively limited successive zones of material transfer along the equipment. The invention relates in particular to a method according to the preamble of claim 1 and an apparatus according to the preamble of claim 8 for carrying out the method.

In order to better control each step of the process, the invention proposes devices to improve the sealing between said zones and in particular to control the flows of molten glass from one zone to another.

The invention is particularly useful for bath kilns with a high production capacity, for example for the production of 600 t / d and more flat glass or 300 t / d and more for hollow glass, but also proves advantageous for smaller installations and thus even more so when such production has increased processing quality requirements and and / or the chemical or thermal homogeneity of the glass produced in the molding equipment.

The choices normally made in the design of industrial equipment and its uses depend on the nature of the manufacture, but their common goal is the independence of the actual smelting control in relation to the independence of the processing of the glass delivered to the molding.

Such independence is achieved, for example, by connecting the melting pool to the treatment tank with an immersed chute, thus both compartments having no connection to the atmosphere, according to the structure used in hollow glass and insulating glass fiber production equipment.

2 86837

Those furnaces that are the subject of a finished record of the Taeolai, usually with a higher production capacity, usually include a corset, i.e., a channel whose vault is not connected to the glass melt, to connect the melting and processing stages.

In certain respects, the use of a gutter has advantages over the use of a corset, as it guarantees the independence of the atmospheres of both compartments and promotes the flow of glass in the melting pool, and may have better and / or colder quality at a level closer to melt bottom than surface. ; but today this can only be designed for furnaces with a flow rate not exceeding 200 t / d, due to the fact that the shear of the gutters is practically limited by the sweetness dimensions of the parts of the vault which the refractory industry is currently able to manufacture.

Thus, flat glass furnaces in the flat glass industry, which usually have a production capacity of 600 t / d and more, cannot use a gutter but rely on a corset, as already shown above. To overcome the disadvantage that could result from the quality of the glass released to the stage of molding, they usually include an extension of the pool for treatment and a very substantial flow of convection current, reaching a flow rate of 5-10 times the surface flow downstream and reaching after crossing the discharge zone, not only the treatment basin but previously the corset itself, and whose bottom current, only at a reduced flow rate, follows the opposite course.

Such a convection system then subjects the refractory parts forming the corset to considerable wear, testing its service life, and proves to be very expensive in terms of energy, as it requires several cycles of thermal cooling and reheating of the glass between processing and processing temperatures before it is molded.

The present invention corrects, or at least substantially reduces, the disadvantages of both of the structures described above, the trough and the corset. This is made possible by providing the method and device according to the invention with the features defined in the characterizing parts of claim 1 and 8, respectively.

The invention relates, firstly, to a continuous process for producing glass in a bath furnace, in which the material to be vitrified is first melted in a zone upstream of the bath furnace specially intended for smelting, said melt gradually reaching and treatment, with the aim of molding, across at least one part of the basin with a cross-sectional contraction, of a type commonly referred to as a corset and hereinafter defined by said method, said method comprising providing a glass flow at the upper level of the opening provided by the corset from the upstream zone and the glass flow. directed downstream towards the upstream of said corset, forming a turn called surface countercurrent in the upstream zone .

Said countercurrent or return current according to the invention is preferably provided by heating of glass controlled from a downstream zone to said opening and said heating is preferably achieved by localized energy dissipation through the Joule effect in the middle of the glass itself by at least one electrode immersed in said melt.

According to a preferred feature of the method of the invention, it comprises a closure device for the atmosphere and / or radiation between said upstream zone of the corset and said downstream zone of the corset, and this closure device is preferably at least adjacent to said outlet or inlet of the corset. to a layer of glazing materials on the surface, and said countercurrent extends at least vertically from the zone of said closure device.

It is preferred that said sealing device leaves free passage to the glass melt at a height of at least 80% of the vertical depth of the melt below the sealing device.

It is further preferred that the removal of the glass outside the upstream zone of the corset, in particular the melting zone, takes place as a stream which is substantially at the central depth of the melt vertically from said closing device.

In addition, the separation plane between the surface countercurrent and the downstream effluent which produces the flow, i.e. the plane at which the horizontal velocity component of the glass is zero, is preferably located vertically from said shut-off device at a distance of at least 90% of the free flow '· To minimize.

In a very preferred embodiment of the method of the invention, the glazed mixture introduced into the furnace basin is distributed to a unit of melt zone upstream of the first shut-off device, and said melt zone is subjected to heating through the Joule effect.

In this case, it is preferably applied to glass which enters the downstream side of said first closure device when heating brings it at least to the normal temperature during processing, thus supplementing the elimination of gas bubbles in melt 86837 5 or entrained by the mixture to be vitrified itself.

The apparatus for the continuous production of molten glass according to the invention is * particularly adapted to carry out the above process and comprises in a general elongate bath a number of compartments passing through the melt in series, each specially designed for one of the main stages of glass production and at least melting and melt processing. at least one part of the basin comprising a cross-sectional contraction of a type commonly referred to as a corset, hereinafter referred to as hereinafter, between said two compartments, and further comprising downstream of said corset in the upstream compartment means capable of providing surface flow in the melt directed downstream to upstream, forming a corset up to said upstream compartment, which is called a surface counter-current, i.e. surface return stream.

Such a current can be obtained by localized heating of a glass melt, which, according to a known heat phonphon effect, produces a convection current schematically around the belt itself, and the device according to the invention preferably comprises at least one electrode immersed downstream of said opening in the melt. side section.

It is preferred that said opening comprises at least one wall at the top, preferably vertically movable, forming a closing device between the upstream and downstream of the melt with respect to the prevailing atmosphere.

Said electrode is preferably located at a distance from said wall which is not more than three times the depth of the lathe at said electrode and preferably includes between half and twice this depth.

Preferably, said wall is further adjustable from above to accommodate the level of the melt and possibly the thickness of the layer of glazing material on its surface, and optionally if necessary to ensure tightness through its mere contact with said layer or immersed in said melt to a depth of up to 20X melt depth.

The homogeneity of said countercurrent over the width of the passage offered to the laws is promoted by the use of a plurality of electrodes, preferably set at the same transverse plane. In the case of a small width of the corset, the electrodes may be horizontal, possibly transverse from one side to the other of said channel, and there are at least two, due to the radius of action of the energy dissipation at this level.

For devices that use a plurality of vertically aligned vertical electrodes, the distance between the extreme electrodes preferably includes between 0.8-1.2 times the width of the corset.

In addition, in order to improve the quality level of the removed glass and release it from flow disturbance, the invention preferably places the electrodes upstream of the closure wall in such a way that the convection circuits they provide can limit the for laws that tu-1θθ to this level.

According to another preferred embodiment of the device of the invention, the corset comprises a threshold having a height of 5 to 7,86837 15% of the height of the melt vertically in the vicinity of the wall of said closure device, promoting said rotation and countercurrent convection circuit control.

According to a particularly preferred embodiment of the device of the invention, this device comprises a melting section on the upstream side of said closing device wall with electrodes capable of projecting into the glass melt across the bottom or walls or even suspended above the melt from the melt in the basin in the zone located upstream of said wall of the closure device.

The wall of the sealing device can ensure its tightness to the atmosphere in this particular embodiment of the invention by extending only to the plane of the melt surface itself due to the layer containing molten powdered glazing materials resting on said wall, while the downstream side is also resisted by electrodes.

In practice, especially if the invention is applied like a "cold vault" in a glass melting apparatus, i.e. where the zone upstream of the barrier wall is completely covered by a layer of glazing materials, countercurrent control should be implemented using glass temperature measures on both sides of said wall, e.g. and to a shallow depth in the melt, for example to a depth of five centimeters: the existence of countercurrent occurs through higher temperatures on the downstream side than on the upstream side of said wall, and a correlation can easily be established between said temperature difference and said countercurrent characteristics.

8 86837

Old equipment can be easily modified to practice the invention. However, when the invention is considered immediately when designing a new furnace, it results in a simpler and less expensive structure, for example by replacing a recessed gutter conventional in bath furnaces with a corset equipped with a vertically movable surface slag boom capable of settling against the layer of glazed materials. Such a shape allows for much more substantial passages and, consequently, the development of high-capacity furnaces, for example more than 400 t / d, with the aim of producing high-quality glass, and guarantees an increased service life of the refractory parts delimiting the outlet.

Other features and advantages of the invention will become apparent from the detailed supplementary description of the invention given below with reference to the drawing: Fig. 1 is a longitudinal sectional side view of a glass cold vault furnace of a known type according to Fig. 2 I-I, and schematically showing the flow of convection currents in the melt section; Fig. 2 is a horizontal section of this same furnace according to Fig. 1 II-II, and in particular the arrangement of the electrodes; Fig. 3 is a longitudinal sectional side view according to Figs. 11ϊ-111 showing the lowering zone of the furnace type of Figs. 1 and 2, the furnace being modified according to the invention by placing a vertically movable hanging wall forming a barrier for the layer of glazing and turning the gutter into a corset; Fig. 4 is a horizontal section of this same zone according to Figs. IV-IV illustrating the arrangement of different electrodes; Fig. 5 is a longitudinal sectional side view according to Fig. 6 V-V and shows a landing zone of a furnace according to the invention comprising a separation corset closed at the top by a vertical barrier with a movable barrier forming a barrier to the floating layer; Fig. 6 is a horizontal section of this same zone according to Figs. 5 to 6, showing in particular the shape of the barrier and the arrangement of the electrodes relative to the barrier; Fig. 7 is a schematic plan view of a furnace subject to a detailed implementation and operation description in accordance with the invention; Fig. 8 is a diagram showing the velocity of the glass for two different flows according to the height of the glass melt vertically from the wall of the closure device and at the longitudinal plane of symmetry of the outlet channel.

A known type of cold vault electric furnace, shown schematically in section in Figures 1 and 2, has a melting basin 1, the base 2 of which is provided with two rows of three vertical electrodes 3 square, as described in FR Patent No. 2,552,073, comprising electrical connections (not shown). not shown) which ensure the dissipation of energy that is clearly similar from one electrode to another. The temperature of the molten glass melt 4 can thus be practically the same value from one zone to another. The layer 5 on the surface of the materials to be vitrified is subjected to each of the electrode-connected convection currents schematically represented by arcs marked by arrows. The fastest of these convection currents follow a umbrella-shaped contour according to the cut through the plane containing the electrode axis: the arm corresponds to the rising currents 6 surrounding the electrode 3 and the shield represents centrifugal radial currents 7 which ensure between existing layer 5.

The centrifugal streams 7 cool in contact with said surface layer 5 while taking 10 86837 of them to load a new law. As they move away from the electrodes 3 that caused them, their velocity decreases, and as they encounter currents 7 or a wall connected to a nearby electrode, they bend into descending currents 8. On their way to the bottom, they generate centrifugal currents 9 that are distributed higher than centrifugal currents. currents 7, and due to the suction phenomenon caused by the rising currents 6, the substance is brought into a new passage of the same convection circuit, usually a tubular passage, similar to that prevailing in the operating washing machine.

The description given herein of a convection tube circuit connected to each electrode is necessarily somewhat schematic. However, it is recognized that when the convection of this melt requires clearly higher rates in the upper zones of the melt, just at the bottom of the melt where the glass is decanted in some way and more specifically at the level of streams 9, there is virtually glass transfer: it passes through the convection circuit shown by the short dashed line in Fig. 1) and its discharge from the basin to the stream 11 gradually ends through a side outlet 12 made in the side wall 13, said opening 12 opening into a downcomer 14 which opens into a handling compartment 15.

This presentation of the interaction of adjacent convection circuits in their equilibrium or mutual support situation, limiting the possibility of material transfer from one circuit to another at the bottom of the melt and subjecting the transferred material to a new circuit with each transverse convection circuit, helps to understand the advantages of the present invention.

Figures 3 and 4 show a furnace forming an extrapolation from that just described with reference to Figures 1 and 2, and this furnace has been the subject of an embodiment of the present invention.

This embodiment comprises placing in the upper part of the basin 21, on the wall 22 on the downstream side against the supports and protruding into the melt 21a, hanging walls 23 <a, b, c) arranged to close the atmosphere of said basin 21 and retain the exposed these partitions 23 are arranged in a regular network of electrodes 25, of which only four three-electrode modules are shown, to form a floating layer on the surface of the homogenization section 26 and provided with two electrodes 25a and 25b symmetrically arranged symmetrically with respect to the longitudinal vertical , and the corset is built to replace the recessed chute of the original oven. This operation, which has been carried out, for example, as a result of the severe destruction of the roof of said trough, after which the trough has been removed, manifests itself in a considerable increase in the shear offered to the removed glass stream. The flows allowed by such a change increase greatly, all the more so as the cooling of the glass is less in the corset than in the trough.

The convection tube circuits 28 connected to the electrodes 25a and 25b of the compartment 26 are adjusted to at least balance the convection circuits connected to the electrodes 25 of the actual compartment 21 and thus resist the direct passage of new glass made by adjacent electrodes 25 ', adjacent to walls 23 <a, b, c). a very effective complementary thread before it reaches the entrance of the corset 27. According to the invention, the glass flow of the convection circuit connected to each of the electrodes 25a and 25b is preferably adjusted to a value at least equal to the flow of the convection circuits of each of the upstream adjacent electrodes 25 '. Due to the higher efficiency of the event due to the convection circuits of the downstream electrodes 25a and 25b, which are placed opposite the upstream electrodes 25 ', the dependent partitions 23 (a, b, c> are placed at a distance smaller than the electrodes 25 (a, b)). of the electrodes 25 ': with the same electric current used in the different electrodes, the downstream convection circuits connected to the electrodes 25 (a, b) at the foot of said partitions, as shown in Fig. 3, distribute stronger currents and hotter glass than those of the upstream electrodes opposite them; Thus, a surface countercurrent is generated at said walls, in which case it is possible to raise said walls so that they only touch the surface of the glass melt, without fear of disadvantages similar to the preamble, such as the direct flow of indigestible substances.

In a preferred embodiment of the invention, the additional electrodes 29 are placed on the downstream side of the corset 27 in its opening 27a preceding the processing section 30.

The electrodes 29 are placed in said compartment 27a at a distance from its upstream wall 31 which is preferably greater than their distance from the downstream wall of the widening compartment 27a forming the corset 27. Thus, the convection circuits connected to the electrodes 29 can to a certain extent increase the power of those connected to the electrodes 25 <a, b).

The electrodes 29 also have the function of ensuring a homogeneous heating of the glass entering the compartment 27a and, if necessary, supplementing its processing by adjusting the rate and maximum level of this heating in accordance with the instructions of FR patent application No. 2,550,523.

Figures 5 and 6 show schematic partial sectional views, respectively, in a longitudinal side view and a horizontal view of a furnace, the structure of which is more precisely defined according to the concept of the invention. The melting basin 40 communicates with the downstream compartment 41, which serves to process the glass prior to molding, through a corset 42 with a hot vault 43 and a widening 42a thereof. Said corset 42, the opening of which is made in the downstream side wall 44 of the basin 40, is provided at the top with a boom 45 which is not or only slightly immersed in the glass melt 46 and is intended mainly to retain the layer 47 on the surface of the glass to be glazed The recess of the boom 45 is preferably adjustable so that it can be mounted at a level at least sufficient under the operating conditions of the furnace to prevent any direct flow of solids from the surface layer 47 towards the corset 42.

Immediately downstream of said boom 45, i.e. at the inlet of the corset 42, according to the invention, two electrodes 48a and 48b are placed at a distance preferably slightly less from the boom 45 than from the electrodes 49a and 49b immediately upstream of said boom.

In addition, the characteristics of the method and size of power supply to the electrodes are selected so that at least those convection circuits connected in pairs opposite the upstream and downstream electrodes 49a / 48a and 49b / 48b, respectively, can be installed to balance each other on the downstream circuits. slightly stronger than the currents of the upstream circuits, according to the principle described previously, and thus settle against the direct flow of new glass made by the electrodes 49a and 49b which are close to the boom 45 immediately upstream thereof.

Under such conditions and due to the nominal flow of the furnace, it is preferred that the boom 45 be raised to a position such that its lower part is no longer embedded in the melt 46 but opposite, for example, from a few millimeters to several centimeters above the interface with the glazing layer. Thus, those convection circuits bent upstream / downstream of the boom are very little disturbed, as is the overall homogeneity of the cycle in the eulatus basin 40. In addition, wear on the boom 45 is very low compared to wear on conventional downspout "roof" parts such as 14 (Figs. and 2), which is generally necessary for this reason to cool very strongly. Finally, this mode of operation facilitates visual control with respect to the balance of the downstream and upstream convection circuits, as well as the control of the applied electric force and its distribution.

When the production of the furnace is reduced, possibly with a controlled "contaminant", it is preferable to reduce the recess of the boom 45 until contact between the melt and the reduced electric force applied to the upstream / downstream bent electrodes is avoided, although electric power is always maintained at a sufficient level to avoid .

When the furnace output is returned to rated operation, the force applied to the downstream electrodes 4Θ <a, b> is re-applied and given priority over the bent upstream electrodes 49 in this operation, and the boom 45 is first lowered again until it penetrates the melt to a depth is at least equal to the required thickness of the surface layer.

According to a preferred embodiment of the furnace, according to the invention, complementary electrodes 4Θ can be placed in the widening 42a of the corset 42, as shown in Figures 5 and 6, on the downstream side of the electrodes 48 (a, b>) with power supply devices and aema such that their combined con -vection circuits may support the convection circuits of electrodes 48 (a, b>: for this purpose, these electrodes 48 are preferably aligned in a straight line in one or more transverse rows, spaced less than the downstream transverse wall 50 of the widening 42a than its upper transverse wall 50). from the wall 51. These complementary electrodes 48 complete the circulation of the lowered glass and are further capable of enabling an improvement in processing by subjecting the convection circuits to the effect of appropriate heating of the incoming glass.

These electrodes also have the function of isolating the electrodes 4Θ <a, b> from the functions applied to the glass processing compartment 41, if necessary, and of ensuring their control of the closing function between the melting section 40 and the processing section 41, limiting the exchange between said compartments to a single flow, and it is preferred that this be limited to a medium level and, if necessary, close to the bottom under the conditions discussed below in the comments to Figure 8.

It should be noted that said flow current, attracting the sum of the base flows from each of the melting cells represented by the convection circuits connected to each melting electrode 49, through a plurality of alternating currents from cell to cell, the temperature at said alternating currents is very uniform over the bottom. The same is true for the flow current over the corset 42, which is thus in excellent conditions for additional processing via the electrodes 48.

Another advantage of the electrodes 48 is in the ease they provide for thermal repairs with the boom 45 or even replacement with a new body if necessary.

16 86837

For such operations, recourse is preferably made to a temporary auxiliary boom formed, for example, of a cooled metal structure, isolating the atmosphere of the corset 42 and the compartment 41 from the atmosphere of the basin 40. In any case, the operations on said boom 45 have no lasting effect on the quality of the separated glass, since the amount of substances on the surface layer which can escape towards the corset 42 is reduced when the electrodes 48 <a, b> are suitably fed.

The implementation of the invention is generally well suited, but proves to be particularly advantageous for cold vault furnaces in which the melting of the load is achieved by bottom or wall kicking electrodes or so-called hanging electrodes, i.e. penetrating the melting melt from above and passing the glazing layer. The latter assumption also preferably relies on either dependent electrodes, but those which are specially protected against the oxidizing atmosphere because they are intended to be located downstream of the boom 45, or bottom transverse electrodes, as well as downstream electrodes 48 <a, b) than with respect to the upstream bent electrodes 49 (a, b) placed immediately upstream of the boom 45 to ensure a certain symmetry with respect to the boom 45 between the bent upstream and downstream convection circuits. The latter version simplifies the structure of the hot vault of the corset 42, where maintenance and electrical connection of the hanging electrodes are more complicated to implement than in the cold vault compartment.

The invention is, of course, all the more advantageous the greater the melting capacity of the furnace due to the limitation of classical gutters described above, which results in the difficulty of producing large refractory parts with sufficient mechanical resistance to heat, especially gutter "roof" elements, i.e. form a vault.

i7 86837

On the other hand, the completion of the corset does not present the same difficulties, as the hanging boom 45 may be a combination of relatively simple shaped pieces, the thinner ones, which are well resistant to temperature fluctuations and generally adapt immediately, are lightly stressed mechanically, leading to corset widths 1.2-3 m for 400 t / d furnaces.

Moreover, the choice of dimensions of the corset 42 is not only related to the maximum production capacity of the furnace and the desired service life of the boom 45, but also to the characteristics of the glass to be produced, the type of operation required for the furnace, etc. (importance of flow variations, etc.)

As for the choice of materials used to build the corset, as well as the boom itself, it also depends on some of these factors. For example, the manufacture of clear glasses generally requires the abandonment of refractory materials rich in C 2 -C 4, which, however, is best to resist corrosion. The effects of this disadvantage on the boom are minimized by limiting as much as possible the electric force applied to the downstream electrodes to provide a hydrodynamic latch to maintain accurately sufficient values of glass countercurrent flow at the surface, boom lower ridge level, and in particular temperature and velocity. . The set of complementary electrodes 48 placed downstream of the latch-forming electrodes then proves to be particularly advantageous in enabling adjustment independent of the action of the latch and the additional processing.

For the sake of clarity, the features of the furnace according to the invention, with a nominal production capacity of 150 t / d glass for the production of flat glass, will now be shown with reference to the schematic plan view of Fig. 7.

ιβ 86837

In a generally rectangular shape, the molten glass base 61 has a bottom area of about 2,45 m, a molten glass discharge corset 62 which opens on the longest side of the melting basin and has a vertical longitudinal symmetry connected to the plane of symmetry of said basin.

The four modules formed by the three electrodes 62 are equipped with a charging surface 61. Said electrodes are formed by cylindrical molybdenum rods placed vertically on the base. Arranged according to a 1.8 m square grid on the side, they are placed in contact with the melt to a length of 0.6-1 m, to a depth of melt that can vary from 1-1.5 m depending on the nature of the glass composition and the use of the furnace.

The electrodes are supplied with a three-phase electric current, the voltage being preferably adjustable without interruption and being able to reach 300 volts between the phases. The coupling mode in the phases (R, S, T) is chosen so as to form two units of six electrodes, the phase order of which is reversed (R, S, T; T, S, R), the neighboring units being symmetrical according to the arrangement known from the aforementioned patent.

The corset 62, with an internal width of 1.5 m, is provided in its opening to the melting basin 61 with a boom 64 formed by a combination of refractory bodies attached at both sides to the wall 61 of its thickness, thus ensuring control of said boom during its adjustment from above, the glazing materials of the layer on the surface and separates the atmosphere between the melting basin and the corset.

About 0.8 m downstream of the boom 64, i.e. approximately in the middle of the length of the corset 62 and in a symmetrical position with respect to the furnace axis, two electrodes 65 of the same type as the electrodes 63 are provided to provide a hydraulic barrier power to the glass which is at the upper level of the channel 62, perpendicular to the boom 64.

Three vertical electrodes 66 transverse to the base are positioned in the widening 62a of the corset 62 preceding the processing section 68 at a position coincident with the positions of the electrodes 48 of the furnace shown in Figures 5 and 6. The force distributed through these electrodes 66 is thus easily adjustable independently of the force of the electrodes 65.

The total available power is about 10,000 kVA in the furnace itself and 300 and 700 kVA in both electrode groups 65 and 65, respectively. With a production capacity of 150 t / d, the total consumption is about 0.9 kWh / kg glass, which is very reasonable for very good processing and for the levels of homogeneity necessary for the manufacture of plate glass, and for the specific production of about 3.3 la-bond per square meter of melt base and per day.

At this flow level, the temperature of the molten glass at the outlet of the melting furnace 61 is set at about 1450 ° C. It is maintained at exactly the same level as the discharge corset 62 is crossed o and raised to about 1530 ° C by electrodes 66 for further processing of the glass to be delivered to the metal surface.

Such a mode of operation is very advantageous for the longevity of the corset: with a similar flow, the traditional gutter of an oven of the same capacity would have been made with about ten times smaller passage and brought with it increased physical erosion and chemical corrosion. In addition, due to the cooling normally required, it would have been subjected to the effect of very heterogeneous temperatures, which also cause very detrimental mechanical disadvantages to its efficiency and longevity.

20 86837

In addition, when the gutter mode is maintained at its limit for use in furnaces with a production capacity of 300-400 t / d, a solution according to the invention proves to propose a corset combined with a surface slag removal boom to hold a surface load in place and equipped with at least one convection circuit electrode. easily conducted to very high capacities by increasing its width.

Fig. Θ shows for two operating systems the variation of the glass rotation speed with respect to the distance at the bottom 71, in a conventional configuration from a furnace according to the invention of the type shown in Fig. 7, where the boom 64 just touches the melt free surface 72, measured vertically downstream of said boom from the lower brush 73 corset with vertical longitudinal symmetry level1 la.

Curve A corresponds to the nominal furnace flow and curve B to the low flow power close to maintenance alone with a saving flame: the part of the diagram to the left of the lower boom downstream of the boom 73, which is considered as the boundary for the surface layer 74, corresponds to the upstream movement (negative flow) and its right side of the movement downstream (positive flow). The furnace flow for a given operating power, being equal to the algebraic sum of the flow rates, positive and negative, is represented by the arithmetic difference of the areas, positive and negative, including between the corresponding curve and the axis of the ordinates, zero-abekis.

In practice, surface countercurrent currents (upstream) are adjusted mainly for a given furnace structure and certain production conditions (furnace dimensions, electrode proportions and locations, melt level, etc.) varying from 2i 86837 to the force downstream of the boom, used in smelting, by monitoring the temperatures measured on both sides of the boom, at the levels taken into account, i.e. especially in the upper and lower regions of the melt.

In the above embodiments of the device of the invention, vertical electrodes are used to provide downstream convection circuits which cause a hydraulic ejection phenomenon, but the invention is not limited at all to this arrangement of electrodes.

In case the equipment is small in tonnage and does not require a very wide corset, electrodes placed horizontally across the walls can be advantageously used, in particular to provide said downstream convection circuits: hydraulic outlet than the eulite power of the vertical electrodes.

Claims (15)

22 86837 A continuous method of manufacturing glass in a bath furnace, wherein the material to be vitrified is first brought into a melt state by melting in a first zone upstream of the basin (21; 40; 61) specially for melting, said melt gradually approaching the downstream zones 30; 41; 68), each of which is generally specifically intended for one of the other phases of the glass manufacturing process, such as processing and treatment for molding, passing through at least a basin section with a reduced horizontal cut in the shape of a corset (27; 42; 62), the manufacturing method further comprising a glass stream upstream, forming a turn on the surface towards the upper zone (21; 40; 61) at the upper level of the inlet of said reduced part, and operating a shut-off device (23 a / b / c; 45; 64) for atmospheric and / or radiation relationship between upstream and downstream, sens u that the shut-off device (23 a / b / c; 45; 64) is located in the vicinity of the inlet opening, extending to the level of the glass melt surface or at least the layer of glazing materials floating on the melt surface, and that said return current reaches at least a zone vertically below the shut-off device. Method according to claim 1, characterized in that the return current is provided by controlled heating of the glass below the inlet (26; 27; 42; 62) and heating is most preferably achieved by localized energy dissipation through the Joule effect inside the glass itself by at least one electrode (25a) b; 48 a / b; 65). A method according to claim 2, characterized in that the sealing device leaves a free passage to the glass melt at a height of at least 80% of the vertical depth of the melt below the sealing device. 23 86837 Method according to Claims 2 and 3, characterized in that the removal of glass from the upstream zone of the corset, in particular from the melting zone, takes place mainly with a stream located at a medium depth vertically below the melting device. Method according to Claims 3 and 4, characterized in that the difference between the surface return current and the discharge current is located at a distance which is at least 90% of the height of the free flow of the glass vertically below the closing device. Method according to one of Claims 2 to 5, characterized in that the glazing mixture introduced into the furnace basin is distributed over the entire zone of the melt upstream of the first shut-off device and that this zone of melt is subjected to heating through the Joule effect inside the glass itself. A method according to claim 6, characterized in that the glass coming downstream of the first closure device is subjected there to the effect of heating, which brings it to at least a normal processing temperature. 1 2 3 4 5 6 7 Apparatus for the continuous production of molten glass, comprising in a elongated bath a number of compartments through which the glass melt passes in series and each of which is specially designed for one of the 4 stages of melting (21, 40, 61) and for melting glass (30, 41, 68), for molding, in which device at least one part of the basin comprises a horizontally limited passage 6 of a cross-section of a corset 5 type (42, 62) between two said compartments, characterized in that it further comprises a limited below the passage inlet, devices (25 a / b; 48 a / b; 65) capable of providing a surface flow in the glass melt directed upstream, forming a surface return up to the upstream section 7, and that the inlet comprises at least one wall (23 a / b / c; 45; 64), which forms a barrier between upstream and downstream with respect to the atmosphere above the melt (21a; 46; 72). Device according to Claim 8, characterized in that the closure moves vertically on a corset. Device according to Claim 9, characterized in that the barrier comprises adjusting devices for height adjustment which enable immersion in the melt to a depth which may be 20% of the depth of the melt. Device according to Claim 8, characterized in that the control devices comprise heating devices (25 a / b; 48 a / b; 65) which cause localized heating of the melt, and preferably comprise at least one electrode embedded in the glass melt downstream of the inlet opening. Device according to claim 11, characterized in that said electrode (25 a / b; 48 a / b; 65) is located at a distance from said barrier (23 a / b; 45, 64) which is at most three times the depth of the melt in the electrode at, most preferably between half of this depth and twice this depth. Device according to Claim 10 or 12, characterized in that the local heating devices comprise a plurality of electrodes arranged in the same vertical transverse plane. Device according to Claim 13, characterized in that the electrodes are arranged vertically, the distance between the extreme electrodes being between 0.8 and 1.2 times the width of the corset-type constraint. Device according to any one of claims 8 to 14, characterized in that it comprises above the barrier (45, 64) and substantially opposite said electrode or electrode array one or more electrodes (25 '; 49 a / b) capable of generating convection circuits which limit the development of convection circuits connected to the former electrodes. Device according to one of Claims 8 to 14, characterized in that it comprises devices (23 a / b / c; 24; 47; 74. for distributing the mixture to be vitrified over the entire zone (21; 40, 61) of the basin located in the barrier (45 , 64) on the upstream side, as well as electrodes (25; 49) which press into the melt in the zone, and devices for supplying electrical energy, the intensity of which is adapted to the melting capacity for the furnace. Device according to one of Claims 8 to 16, characterized in that the corset-type restriction comprises a threshold with a height of 5 to 15% of the depth of the melt, close to the vertical plane passing through the barrier (23 a / b; 45, 64).